Many human and animal diseases, including cancer, are associated with changes in cellular immunity (delayed hypersensitivity) and in production of lymphokines (non-antibody mediators of cellular immunity). It has been difficult in the past to quantitate accurately in vitro these changes in cellular immunity, a difficulty which might be overcome if there were available an antibody specific for a lymphokine associated with cellular immunity; this antibody could be used to develop a radioimmunoassay to measure in vitro cellular immunity to tumor and other antigens. Macrophage agglutination factor (MAggF) is a lymphokine derived from antigen stimulated guinea pig lymph node cells with cellular immunity to antigen; similar activities have been reported in appropriately stimulated culture supernates of human and animal mononuclear cells. The chemical and physical nature of this lymphokine are poorly understood and its exact role in cellular immune reactions in vivo remains undefined. The proposed project will attempt to isolate guinea pig MAggF from concentrated culture supernates of antigen-stimulated guinea pig lymph node cells by sequential fractionation of these supernates with gel chromatography and polyacrylamide-agarose gel electrophoresis. Isolated and purified active MAggF will be characterized and used to raise specific antisera in rabbits. The specificity of these antisera for MAggF will be determined. The characterized antisera will then be used to evaluate the role of MAggF in in vivo cellular immunity and to quantitate in vitro models of these reactions.